1. Field of the Invention
The present invention relates to a multi-core fiber having a plurality of cores respectively extending along a predetermined axis.
2. Related Background Art
Multi-core fibers, constituted so as to integrally surround a plurality of cores with a cladding region in order to realize higher capacity in optical transmission, are known.
For example, in a multi-core fiber described in IEICE Electronics Express, Vol. 6, No. 2, pp. 98-103 (Document 1), when the center-to-center spacing of the cores is 30 μm, concerning the power transfer ratio between cores adjacent to each other, sufficiently small crosstalk can be realized by changing the difference in relative refractive index difference Δ (hereinafter, referred to as core Δ) of a core from a cladding between cores adjacent to each other to be slight (for example, 0.005%). By this, a multi-core fiber with a cladding diameter of 125 μm having three types of cores with different core Δ can be realized. However, bending of the fiber is not considered in Document 1. In the result of fabricating a multi-core fiber in accordance with Document 1, it was reported that the theretical value and the measured value of crosstalk remarkably differ from each other, and it was considered that this matter was caused by a core diameter whose size is off from a designed size. However, an effect due to bending was not considered.